1. Field of the Invention
The invention concerns an optical storage with an optical storage medium consisting of a plurality of storage fields arranged in matrix fashion, wherein each storage field of this storage field matrix comprises a storage position matrix consisting of a plurality of storage positions arranged in matrix fashion, and an X/Y deflection system for random-addressing a storage position of a storage field of the storage field matrix responsive to an X- and a Y-control signal such that a light beam impinging on the X/Y deflection system is directed to a storage position of a storage field of the optical storage medium corresponding to the position of the X/Y deflection system resulting from the two control signals.
2. Description of the Prior Art
Matrix optical storage is known from U.S. Pat. No. 3,996,570. A disadvantage of the known optical storage is that two separate optical devices are required for reading items of data from and writing them into the storage medium. The use of an optical read means and an optical write means separate therefrom with regard to design and function leads to an elaborate design of the optical storage.
The write means used to write data into the optical storage medium has a laser, acting as a light source, which emits a spatially coherent and collimated light beam. Having passed through the electro-optic modulator, the laser beam is directed to the two-stage X/Y deflection system used to random-address the individual storage positions of the storage medium. A storage field deflecting means of the X/Y deflection system selects one of a plurality of storage fields arranged on the storage medium in matrix fashion. An acousto-optic storage position deflecting means of the X/Y deflection system, preceding the storage field deflecting means, serves to random-address a particular storage position of the storage field selected by the storage field deflecting means. Having passed through the two-stage X/Y deflection system, the deflected laser beam is directed to a semi-transparent mirror where it is reflected. The reflected light beam is led via a matrix lens array, by which it is focused, to the storage medium. The influence of the laser beam on a selected storage position of a storage field changes its physical state which is detected during reading by the read means of the optical storage.
The optical read means comprises a matrix light diode array positioned behind the storage medium and fitted with one light diode for each storage field of the storage field medium. The individual light diodes of the matrix light diode array are controlled by the control unit of the optical storage for random-addressing a storage field of the storage medium. The light emitted by a light diode of the matrix light diode array passes through the illuminated storage field of the storage medium to be focused by the matrix lens array preceding the storage medium and to be directed through the semi-transparent mirror to a lens system. This lens system enlarges the image of the illuminated storage field of the storage medium, which is generated by the light diode of the matrix light diode array. This elaborate lens array is necessary for sensing the individual storage positions of the imaged storage field of the storage medium by a detecting means of the optical read means. The detecting means has a plurality of detectors arranged in matrix fashion, the number and arrangement of which correspond to the configuration of the storage positions of one of the storage fields. Apart from separate read and write operations and the previously described disadvantages, this known storage has a number of unfavorable characteristics so that it fails to meet the requirements of up-to-date data processing systems. The storage field deflection means of the optical write means is made up of two mechanically rotatable mirrors which are adjusted by stepper motors. Such mechanical positioning of the rotatable mirrors, used for random storage field deflection, reduces the access speed to a particular storage field of the storage medium.
In addition, the mirror setting is not satisfactorily reproducible. Positioning tolerances which adversely affect the density of the storage positions of the storage medium are caused by mechanically positioning the rotatable mirrors of the storage field deflecting means. The individual storage positions of the storage medium have to be physically spaced such that the laser beam, taking account of positioning tolerances, invariably remains within the area the storage position assumes on the storage medium. In view of the tolerances resulting from mechanical beam positioning, it is impossible to use a highly integrated storage medium in which two neighboring storage positions are arranged closely adjacent to each other. In such a case, the positioning errors occurring in the known X/Y deflection system would lead to faulty access to storage positions and thus to faulty data.
A further disadvantage of the known optical storage in data processing systems is that the data to be stored in the individual positions of the storage medium can only be written in a bit-serial fashion. As a result, only one storage position can be accessed by suitably controlling the storage position and/or the storage field deflecting means. Such time-serial access to the positions of the storage medium falls short of the requirements to be met by the operating speed of up-to-date data processing systems and their interacting optical storages.